This is a review of a decision of the court of appeals, In re Interest of Z.J.H., 157 Wis. 2d 431, 459 N.W.2d 602 (Ct. App. 1990). In its decision, the court of appeals affirmed a summary judgment of the circuit court for Outagamie county, Judge Dee R. Dyer, dismissing an action by the petitioner-appellant-petitioner (Sporleder) seeking physical placement or visitation of Z.J.H., the adopted son of the respondent (Hermes). Sporleder seeks review of that decision, pursuant to sec. (Rule) 809.62, Stats.
Four issues are raised on this review: (1) Is Sporleder, who is not a natural or adoptive parent of Z.J.H., entitled to custody or physical placement of Z.J.H. under the in loco parentis doctrine?; (2) Does sec. 767.245(1), Stats., entitle Sporleder to visitation rights to Z.J.H. absent an underlying action affecting the family?; (3) Is a co-parenting contract between Sporleder and Hermes, the adoptive parent, enforceable by the courts when it concerns the physical placement of the child or visitation rights to the child?; and (4) Is Hermes equitably estopped from denying that Sporleder is an equitable parent of Z.J.H., and therefore entitled to custody of Z.J.H. or visitation with Z.J.H.?
We first conclude that Sporleder does not have standing to acquire custody1 of Z.J.H. There is no allega*1007tion that Hermes is either unfit or unable to care for Z.J.H., and Sporleder has not established that compelling reasons exist for awarding custody to a third party. Second, we conclude that Sporleder is not entitled to visitation rights with Z.J.H., because there is no underlying action affecting the family. Third, we conclude that the co-parenting contract between Sporleder and Hermes is unenforceable. The rights to custody and visitation are controlled by statutory and case law, and cannot be determined by contract. Finally, we conclude that Hermes is not equitably estopped from denying custody and visitation to Sporleder.
The relevant facts follow. Sporleder and Hermes lived together as companions for approximately eight years. After an unsuccessful attempt to have a child through the artificial insemination of Sporleder, they decided that Hermes would adopt a child. In March 1988, Z.J.H., born January 19, 1988, was placed in their home as a result of a pre-adoptive placement by an adoption agency. Sporleder provided the primary care for Z.J.H., while Hermes worked outside the home. On October 25, 1988, the parties entered a co-parenting agreement, in which they agreed, among other things, that if they separated they would determine the physical placement of Z.J.H. through mediation, and that the non-placement party would have reasonable and liberal visitation rights to the child.
Sometime in October 1988 the parties separated.2 Hermes then formally adopted Z.J.H. in November 1988, *1008and subsequently prohibited Sporleder from seeing Z.J.H.
In March 1989, Sporleder brought an action in the Outagamie county family court, seeking visitation rights or physical custody of Z.J.H., and seeking to enforce the co-parenting agreement. The family court commissioner granted visitation rights to Sporleder, and deferred to the circuit court on the other issues. The circuit court subsequently granted summary judgment for Hermes, on the grounds that Sporleder did not enjoy the legal status of parent, and had no standing to exercise these rights under Van Cleve v. Hemminger, 141 Wis. 2d 543, 415 N.W.2d 571 (Ct. App. 1987). The circuit court also found that the agreement was void as against public policy, and that Hermes was not equitably estopped from denying Sporleder's status as a parent.
The court of appeals affirmed the judgment of the circuit court, concluding that Sporleder was not entitled to custody or visitation rights to Z.J.H. We review the court of appeals decision pursuant to sec. (Rule) 809.62, Stats.
hH
We first determine that Sporleder does not have standing3 to sustain an action to obtain custody of *1009Z.J.H. In reaching this conclusion, we first examine who has standing to bring an action for custody under the custody statute, sec. 767.24, Stats. Next, we examine whether Sporleder qualifies for such status under the statutory and common law of the state.
We conclude that, according to sec. 767.24(1), Stats., and this court's decision in Barstad v. Frazier, 118 Wis. 2d 549, 348 N.W.2d 479 (1984), a non-parent may not bring an action to obtain custody of a minor child unless the natural or adoptive parent is unfit or unable to care for the child, or there are compelling reasons for awarding custody to a third party. Barstad, 118 Wis. 2d at 568. See also J. McCahey, Child Custody and Visitation Law and Practice, sec. 11.03[1] (1991) (discussing the Barstad rule).
The general provisions concerning child custody and physical placement are found in sec. 767.24(1), Stats.4 This section describes the circumstances under which the court may make custody and placement determinations for minor children. This case does not involve an action for annulment, divorce or legal separation between the parties. Conceivably, however, Sporleder *1010may bring an action under sec. 767.02(l)(e),5 if Z.J.H. is her "minor child."
Setting aside the question of Sporleder's status as a parent for now, it is helpful to examine the circumstances under which a non-parent can acquire standing to obtain custody of a minor child. First, under sec. 767.24(3), Stats., a relative can acquire custody, "[i]f the interest of any child demands it, and if the court finds that neither parent is able to care for the child adequately or that neither parent is fit and proper to have the care and custody of the child,1' under a child in need of protection or services (CHIPS) proceeding. Sporleder concedes that Hermes is not unfit or incapable of taking care of Z.J.H., and hence sec. 767.24(3) does not apply to this case.
Second, a third party can acquire custody of a minor child if "compelling circumstances" exist, which necessitate awarding custody to one other than the child's parent. We stated, in Barstad: *1011Barstad, 118 Wis. 2d at 568. We find no such conditions or extraordinary circumstances present here.
*1010We conclude that the rule to be followed in custody disputes between parents and third parties is that a parent is entitled to custody of his or her children unless the parent is either unfit or unable to care for the children or there are compelling reasons for awarding custody to a third party. Compelling reasons include abandonment, persistent neglect of parental responsibilities, extended disruption of parental custody, or other similar extraordinary circumstances that would drastically affect the welfare of the child.
*1011Sporleder contends that summary judgment was inappropriate in this case, because she was never given the opportunity to show that compelling circumstances existed, which would entitle her to custody over Hermes. Applying the procedure to be used in reviewing summary judgment orders,6 we conclude that summary judgment was appropriate in this case. Reviewing the case as the circuit court did, and applying the standards of sec. 802.08(2), Stats., we conclude that the pleadings, depositions, answers to interrogatories, and the admissions on file, together with the affidavits do not establish a genuine issue of material fact. The parties do not dispute that they entered a co-parenting contract. Neither do they disagree that Sporleder had a "parent-like" relationship with Z.J.H. Hermes, in her motion for summary judgment, conceded as much. There are no disputed material facts, or undisputed facts from which reasonable alternative inferences may be drawn. See Grams, 97 Wis. 2d at 338. The crucial question is whether these facts represent "compelling circumstances." We conclude, as a matter of law, that they do not.
Clearly, this case does not involve abandonment, persistent neglect of parental duties, or extended disruption of parental custody. Although Sporleder may have been the primary care provider, Z.J.H. was not separated from Hermes. Additionally, we do not find "similar extraordinary circumstances." Barstad, 118 Wis. 2d at *1012568. This case is vastly different from the case Sporleder primarily relies on, LaChapell v. Mawhinney, 66 Wis. 2d 679, 225 N.W.2d 501 (1975). In LaChapell, custody of two minor children was awarded to the children's grandparents over their natural father. In that case, the father had not lived with the children for eight years, had not displayed any interest in them, and had only visited them twice. LaChapell, 66 Wis. 2d at 684. Here, we find no such compelling circumstances to justify awarding custody to a third party.
Although Sporleder had cultivated a "parent-like" relationship with Z.J.H., and expected that relationship to continue, the focus of our decision in Barstad was that compelling circumstances existed when a deficiency existed in the relationship of the child with the natural parent that drastically affected the welfare of the child. Barstad, 118 Wis. 2d at 568. Such is not the case here.
Hence, we conclude that the conditions under which a third party can acquire custody of a minor child are not satisfied in this case. Unless Sporleder qualifies as a "parent" of Z.J.H., Z.J.H. is not a "child of the parties," sec. 767.24(1), Stats., and Sporleder does not have standing to acquire custody.7
Our second inquiry in resolving the custody issue is whether Sporleder may have standing as a "parent." "Parent" is undefined in ch. 767, Stats., although the term is used periodically throughout (e.g., sec. 767.25, *1013Child Support; sec. 767.327, Moving the Child's Residence Within or Outside the State).
Sporleder claims the status of a parent, based on a theory of "in loco parentis."8 Sporleder relies on In re Custody of D.M.M., 137 Wis. 2d 375, 404 N.W.2d 530 (1987), in which we addressed sec. 767.245(4), Stats. 1985-86 (now sec. 767.245(1)), Visitation. In D.M.M., we stated, in dicta: "In Webster's Third New International Dictionary (1967), in addition to other meanings, parent is defined as 'a person standing in loco parentis although not a natural parent.' " D.M.M., 137 Wis. 2d at 385.
Our holding in D.M.M., however, is unrelated to our holding today. In D.M.M., the issue was whether the circuit court could grant visitation rights to any persons other than those named in sec. 767.245(4), Stats. 1985-86, namely, parents, grandparents or great grandparents. In D.M.M., a visitation dispute arose between F.P.R., D.M.M.'s aunt, and J.M., D.M.M.'s mother. *1014F.P.R. had been D.M.M.'s court-appointed guardian until June 5, 1984. When the guardianship was discharged, the circuit court also denied visitation rights to F.P.R. After F.P.R. petitioned for visitation rights, J.M. moved to dismiss on the ground that F.P.R. had not stated a claim under sec. 767.245(4), because she was not a grandparent or a great grandparent.
We found that the use of the term "parent" in sec. 767.245(4), Stats. 1985-86, was ambiguous, and could also include someone in loco parentis. D.M.M., 137 Wis. 2d at 385. However, we also concluded that the statute could alternatively be limited to natural parents only. Id. at 386. Ultimately, we left "parent" undefined, concluding that F.P.R. had standing to acquire visitation rights under sec. 767.245(4), based on our conclusion that the legislature did not intend to supplant the common law by limiting visitation to parents, grandparents and great grandparents. Id. at 390. Hence, F.P.R. acquired standing to pursue visitation rights not as a "parent," but as an "other person."9
This court has never applied an "in loco parentis" approach to custody actions. Such a theory is inconsistent with this state's adherence to the "parental preference" standard (also called the "parental right" standard) in the resolution of custody disputes. See J. McCahey, supra, at sec. 11.03[1]. See also Barstad, 118 Wis. 2d at 568-69. The "parental preference" rule gives great deference to the rights of parents such as Hermes to raise their children. Id. See also Ponsford v. Crute, 56 Wis. 2d 407, 413, 202 N.W.2d 5 (1972); Sommers v. Sommers, 33 Wis. 2d 22, 26, 146 N.W.2d 428 (1966). *1015While this rule recognizes the rights of children, it also assumes that normally it is in the best interests of the child to be raised by his or her parent. In Barstad, we stated, " [u]nder ordinary circumstances, a natural parent has a protected right under both state law and the United States Constitution to rear his or her children free from governmental intervention." Barstad, 118 Wis. 2d at 567. Barstad recognized the constitutional rights of the natural parent, rather than the third party. In United States Supreme Court cases which have found a constitutionally protected interest in a parental relationship with the child, each case has involved a natural parent. See Caban v. Mohammed, 441 U.S. 380 (1979); Stanley v. Illinois, 405 U.S. 645 (1972). While these and other cases (see, e.g., Michael H. v. Gerald D., 109 S. Ct. 2333 (1989); Lehr v. Robertson, 463 U.S. 248 (1983); Quilloin v. Walcott, 434 U.S. 246 (1978)) have required a relationship beyond a biological one to create a constitutionally protected interest, none has suggested that an individual who stands in loco parentis acquires such an interest. On the contrary, to the extent that we award custody rights to one who stands in loco parentis as Sporleder urges, we diminish the rights of legal parents such as Hermes.
Sporleder cites Thelen v. Catholic Social Services, 691 F. Supp. 1179 (E.D. Wis. 1988), for the proposition that individuals who do not have a biological relationship with the child can still have a protected liberty interest in that relationship under the Fourth Amendment to the United States Constitution.
Thelen is distinguishable from this case. In Thelen, the court stated: "The narrow issue before the Court is whether prospective adoptive parents with whom a child has been placed have a Due Process right under the United States Constitution to a hearing prior to the *1016removal of the child during the initial six-month period of placement." Thelen, 691 F. Supp. at 1180. That court concluded, "the prospective adoptive couple has a limited, but not wholly insignificant, constitutionally protected liberty interest in their family unit during the initial six-month period that a child is placed in their home." Id. at 1185. The Thelens had a reasonable expectation under the adoption statutes that they would eventually acquire legal parental status of the to-be-adopted child. Id. at 1184. Sporleder may have had a reasonable expectation that her status as care provider would continue, but there was no indication that she would acquire legal parental status. Hence, hers is not a protected liberty interest.
The legislative history behind ch. 767, Stats., also supports this conclusion. Sections 767.24 and .245 were both substantively revised in 1987. 1987 Wis. Act 355, secs. 25-38. Section 767.24(1) (c) was renumbered to sec. 762.24(3)(a), and amended to refer to "parent,” rather than "party." Section 28. Section 767.245(4) was renumbered to sec. 767.245(1), and amended to include a "person who has maintained a relationship similar to a parent-child relationship with the child," as persons who may petition for visitation rights. Section 38. This language is particularly instructive. It demonstrates that the legislature did not intend to preclude such persons from visitation rights, as we stated in D.M.M. It also demonstrates that the legislature was cognizant of the concerns of individuals such as F.P.R. and Sporleder. As we stated in State v. Welkos, "where a statute with respect to one subject contains a given provision, the omission of such provision from a similar statute concerning a related subject is significant in showing that a different intention existed." Welkos, 14 Wis. 2d 186,192, 109 N.W.2d 889 (1961). The legislature could have, but *1017did not broaden sec. 767.24(1) to include parent-like individuals such as Sporleder. Nor did the legislature broaden sec. 767.24(3) (a) to include these individuals. Finally, the legislature could have easily included a definition of "parent" in sec. 767.001, a definitional section created by 1987 Wis. Act 355. See sec. 11.
This definitional omission is significant in light of sec. 48.02, Stats. Section 48.02 is a definitional section in the Children's Code, and provides: " 'Parent' means either a biological parent, a husband who has consented to the artificial insemination of his wife under s. 891.40, or a parent by adoption." Section 48.02(13). While this definition applies to ch. 48, and not specifically to ch. 767, sec. 48.02 in general is referenced throughout ch. 767. (See, e.g., sec. 767.001(2)(b); sec. 767.24(3)(a)). While we do not suggest that the definition of "parent" in sec. 48.02(13) controls every reference to "parent" in ch. 767, the fact that sec. 48.02 is referenced in ch. 767 is evidence of the fact that the legislature was aware of sec. 48.02 at the time 1987 Wis. Act 355 was enacted, and could have created a distinct definition of "parent" under ch. 767, had it so intended.
In holding that Sporleder does not have standing to obtain custody of Z.J.H., we also recognize the public policy consideration of limiting the number of individuals with whom a child is placed, in order to promote stability in that child's life. Were we to permit individuals standing in loco parentis to obtain custody, as Sporleder urges us to do, we would open the doors to multiple parties claiming custody of children by virtue of their in loco parentis status. Without limitations as we have discussed today, a child could have multiple "par*1018ents,"10 and could find himself or herself subject to multiple custody and visitation arrangements. Although Sporleder suggests a framework wherein the group of "parents" would take into consideration the intent of the natural/adoptive parent, we nonetheless envision situations where a child could be in such an unstable environment. It would be virtually impossible to ensure equity to all parties and protect the best interests of the child under such a scenario. The California Court of Appeals appropriately stated: "We do not, however, agree that the only way to avoid such an unfortunate situation [the suffering a child such as Z.J.H. may endure as a result of his separation from Sporleder] is for the courts to adopt appellant's novel theory by which a nonparent can acquire the rights of a parent, and then face years of unraveling the complex practical, social, and constitutional ramifications of this expansion of the definition of parent." Nancy S., 279 Cal. Rptr. at 219. While our decision today may result in occasional unfortunate consequences for minor children who have developed relationships with individuals claiming standing under the doctrine of in loco parentis, the legislature deliberately spared the legal system from an obligation to discern a just result from among the myriad of circumstances in which individuals could claim rights under the in loco parentis doctrine.
Most of the cases dealing with custody disputes involve biological parents. Hermes is the adoptive mother of Z.J.H. As such, she has all the "rights, duties and other legal consequences of the natural relation of child and parent." Section 48.92, Stats. These "rights, duties and other legal consequences" include the right to *1019custody as a parent of the child, sec. 767.24(1), Stats., and the freedom from governmental intervention unless sec. 767.24(3)(a) or other compelling circumstances apply. Barstad, 118 Wis. 2d at 567. The child has a right of inheritance from his adoptive parent under sec. 851.51, Stats. In essence, Hermes has the rights of a natural parent, and is entitled to the presumption that as between a natural parent and a third party, the " 'best interests of the child' lie with the natural parents' exercise of custodial rights." State ex rel. Lewis v. Lutheran Social Services, 59 Wis. 2d 1, 13, 207 N.W.2d 826 (1973). Sporleder is not entitled to this presumption as she is not legally a "parent" of Z.J.H.11
*1020hH l-H
Sporleder is also not entitled to visitation rights under sec. 767.245(1), Stats.12 While this section does not specifically preclude such an action by a third party, a review of our case law leads to the inescapable conclusion that there must be an underlying action affecting the family unit before the provisions of sec. 767.245(1) are implicated. As we have held, Sporleder does not have standing to bring a custody action. Additionally, there is no other action affecting the family unit (e.g., divorce, CHIPS) in this case. We discussed the predecessor statute to sec. 767.245(1), sec. 767.245(4), Stats. 1985-86, in In re Marriage of Soergel, 154 Wis. 2d 564, 453 N.W.2d 624 (1990). Although the language in the predecessor statute did not refer to "person[s] who [had] maintained a relationship similar to a parent-child relationship with the child," we recognized that this language was added by the legislature to expand this provision to include such individuals. Soergel, 154 Wis. 2d at 567 n.2.13 There is no indication that the legislature intended to allow visitation against parental wishes in the absence of actions affecting the marriage. We concluded, in Soergel, that the legislature intended to codify earlier judicial *1021decisions in enacting sec. 767.245(4). See Weichman v. Weichman, 50 Wis. 2d 731, 184 N.W.2d 882 (1971); Ponsford, 56 Wis. 2d 407. We stated, "[t]he history of sec. 767.245(4), Stats., shows the legislature intended to codify this court's decisions in Weichman and Ponsford; therefore, this provision applies in divorce or custody cases or in other actions affecting the marriage." Soergel, 154 Wis. 2d at 573. This case, as in Soergel, does not involve an action affecting the marriage.
We also addressed the negative impact that a grant of visitation rights would have on an adoptive parent, such as Hermes. We stated, "adoption effects 'a complete substitution of rights, duties, and other legal consequences of the natural relation of child and parent and kin with those same rights, duties, and legal consequences between the adopted person and the adoptive parents and kin.' " Id. (quoting Estate of Topel, 32 Wis. 2d 223, 227, 145 N.W.2d 162 (1966)). One of the rights an adoptive parent acquires, we stated, "is the right to determine whether a relationship with the grandparents, or any other person, is contrary to the child's best interests." Id. at 574. Here, as there, we conclude that it is for the adoptive parent Hermes, not the court, to decide whether visitation with Sporleder is in Z.J.H.'s best interests, and sec. 767.245(1), Stats., was not intended to interfere with that right. See id.14
*1022Finally, in Soergel, we referred approvingly to Van Cleue, 141 Wis. 2d 543, a case in which the court of appeals defined the purpose and scope of the visitation statute. Soergel, 154 Wis. 2d at 571. In Van Cleue, the court of appeals stated, " [i]t is obvious from these analy-ses that the legislature did not intend that the state intervene in the parents' decision regarding their children's best interests when the family unit is intact." Van Cleue, 141 Wis. 2d at 549. Consequently, the court of appeals refused to extend the application of sec. 767.245(4) beyond cases where an underlying action affecting the family unit had been filed. Id. In arguing that Hermes and Z.J.H. do not represent an "intact family," Sporleder misses the point of Van Cleue and Soergel. The rationale behind these cases was that the legislature did not intend to override a parent's determination of visitation unless an underlying action affecting the family unit had been filed, because in such an instance, ordering visitation with non-parents may help to mitigate the trauma and impact of a dissolving family relationship. Soergel, 154 Wis. 2d at 571-72; Van Cleue, 141 Wis. 2d at 549. The presence of an intact family unit merely signals the absence of a dissolving family relationship.
In this case, whether the conclusion results from (a) the characterization of Hermes and Z.J.H. as an "intact family unit," or (b) the absence of an underlying action *1023affecting the family unit, the same result occurs: there is no authority for Sporleder to petition for visitation rights.
While Sporleder insists that the legislature intended to change the purpose and scope of sec. 767.245(4), Stats. 1985-86, when it was amended, we find her arguments unpersuasive. First, the legislature can be presumed to have been aware of Van Cleve when sec. 767.245 was amended in 1987 (1987 Wis. Act 355). See Zimmerman v. Wisconsin Elec. Power Co., 38 Wis. 2d 626, 634, 157 N.W.2d 648 (1968). The legislature could have, had it so intended, amended sec. 767.245(4) to allow visitation rights to such third parties in light of Van Cleve's finding that the legislature did not intend that the state intervene in the parents' decision regarding their child's best interests when the family unit was intact and no underlying actions affecting the family unit had been filed. Van Cleve, 141 Wis. 2d at 549. Second, in Soergel, we recognized that the statute had been amended to include stepparents and individuals who had maintained a parent-like relationship with the child. We recognized that the language of sec. 767.245(4) was amended for the very purpose of granting visitation rights to these individuals. Soergel, 154 Wis. 2d at 567 n.2. The intent, therefore, was to include stepparents and parent-like individuals in the group of people who may qualify for visitation rights to a minor child when an underlying action affecting the marriage existed. The legislature did not express an intent to grant this group visitation rights to a child in an intact family unit.
HH HH HH
We next conclude, as did the court of appeals, that rights to custody and visitation are controlled by statu*1024tory and case law, and cannot be contracted away. "When the legislative will is expressed in peremptory terms of a statute it is paramount and absolute and cannot be varied or waived by the private conventions of the parties." Grams v. Melrose-Mindoro Jt. School Dist. No. 1, 78 Wis. 2d 569, 578, 254 N.W.2d 730 (1977). Because we conclude that the legislative intent grants custody and visitation rights to non-parents only under the circumstances described above, the contract is void to the extent it purports to award custody or grant visitation rights to Sporleder.
Additionally, in light of the societal and constitutional interests in maintaining the relationship between a natural or adoptive parent and that parent's child, public policy concerns militate against contractual provisions affecting this relationship.
This court has recognized the public interest in protecting not only the rights of the natural or adoptive parent, but of the family unit as well. Barstad, 118 Wis. 2d at 568. Hermes, as the legal parent, has all the rights and responsibilities which the law confers. She is legally responsible for the well-being of Z.J.H., and there is no indication that she has not fulfilled that responsibility. We have said that the court should not displace a fit and able parent for one who does not have the legal status of a parent, even if such a person could do as good a job or even a better job of parenting. See id. at 567-68. The co-parenting agreement, to the extent that it purports to award custody or grant visitation rights to Sporleder, is inconsistent with legislative intent behind the custody and visitation statutes, which prefer parents over third parties. It is also inconsistent with our conclusion that, unless circumstances compel a contrary conclusion, it is in Z.J.H.'s best interest to live in his legal parent's home. See LaChapell, 66 Wis. 2d at 683.
*1025We stated, in Stickles v. Reichardt, 203 Wis. 579, 582, 234 N.W.2d 728 (1931), "in the absence of a statute, contracts of a parent by which a parent attempts to transfer permanently the custody of his child to another are invalid as contrary to public policy." While the purported transfer in Stickles would have not resulted in a permanent transfer of the child, it would "if given effect impair the adoptive parents' right to the custody of their child and might in its effect greatly impair the new parent-child relationship with very undesirable consequences to the child." Stickles, 203 Wis. at 582. Finally, we stated, ”[t]he adoptive parents can no more barter away their rights in their adopted child or modify its status by contract than could a natural parent under the same or similar circumstances." Id. at 583.
We conclude that because of the public interest in maintaining a stable relationship between a child and his or her legal parent, the co-parenting agreement, to the extent that it purports to award custody or grant visitation rights to Sporleder, is unenforceable. While we recognize that Sporleder may have had a reasonable expectation that she would have continued contact with Z.J.H. under the agreement, enforcing the agreement would be contrary to legislative intent and the public interest.
HH <
Finally, Hermes is not equitably estopped from denying that Sporleder is a parent of Z.J.H. The legal effects and consequences of statutory limitations cannot be avoided by estoppel. Grams, 78 Wis. 2d at 578. See also Utschig v. McClone, 16 Wis. 2d 506, 509, 114 N.W.2d 854 (1962) (quoting 19 Am. Jur. Estoppel, 639 *1026sec. 40) ("The effect of an estoppel in pais is to prevent the assertion of what would otherwise be an unequivocal right. . . . Such an estoppel operates always as a shield, never as a sword. . . . [A]nd it does not of itself create new rights."). Sporleder cannot use the theory of equitable estoppel to create rights to custody or visitation to Z.J.H.
The primary case upon which Sporleder relies, In re Paternity of D.L.H., 142 Wis. 2d 606, 419 N.W.2d 283 (Ct. App. 1987), is dissimilar. In D.L.H., the court of appeals concluded that, for purposes of establishing a right to a relationship with the child born to his wife but fathered by another man, the husband may utilize the status of "equitable parent"15 to assert an equitable estoppel defense against the child's mother instituting paternity proceedings against him. D.L.H., 142 Wis. 2d at 617. In D.L.H., the husband used the equitable estop-pel defense as a shield, to protect his right to a relationship with the child. Such is not the case here. Equitable estoppel has not been invoked in Wisconsin against a natural/adoptive parent for the purpose of awarding custody to a non-parent.16 See Nancy S., 279 Cal. Rptr. at 217-19.
*1027We also distinguish In re Marriage of D.L.J. and R.R.J., 162 Wis. 2d 420, 469 N.W.2d 877 (Ct. App. 1991). In that case, a child (J.L.J.) was born to D.L.J. and R.R.J. while they were married. During divorce proceedings, D.L.J. (the mother) moved the family court commissioner to order R.R.J. (the husband) to submit to blood tests, on the ground that D.L.J. had had sexual intercourse with two other men during the conceptive period and did not believe that R.R.J. was the father of J.L.J. (It was not until R.R.J. filed a motion for custody of J.L.J. that D.L.J. first claimed that R.R.J. was not the child's natural father.) The blood tests excluded R.R.J. as J.L.J.'s father, and the family court commissioner terminated visitation between J.L.J. and R.R.J. The circuit court, finding that R.R.J. was not the biological father of J.L.J., also denied visitation between J.L.J. and R.R.J.
Subsequently, the court of appeals held that R.R.J. had the status of "equitable parent," and that D.L.J. was equitably estopped from seeking a declaration that R.R.J. was not J.L.J.'s natural parent. D.L.J., 162 Wis. 2d 420, 426, 427. The fact that R.R.J. had the status of a "natural parent" prior to D.L.J.'s motion and the subsequent blood test makes this case distinguishable.17 Sporleder never had the status of "natural parent." Unlike D.L.J., there was no revelation by Hermes that *1028Sporleder was not a parent to the child. In contrast, Sporleder never believed that she was a "natural parent" to Z.J.H. Although Sporleder may have assumed parent-like responsibilities for the care of Z.J.H., at no time did she or Hermes believe that she had the legal status of parent. Consequently, she did not acquire the status of "equitable parent" as did R.R.J.
By the Court. — The decision of the court of appeals is affirmed.
The co-parenting contract which the parties entered refers *1007only to physical placement of Z.J.H. In her brief, Sporleder argues that she is entitled to legal custody and physical placement. Section 767.24(1), Stats., treats legal custody and physical placement similarly. In this opinion, we use the term "custody" to refer to both legal custody and physical placement.
The agreement was executed after Sporleder and Hermes *1008had separated. Hermes asserted, in her defense to the validity of the agreement, that she had signed it under duress caused by Sporleder's threats to interfere with her adoption of Z.J.H.
The concept of standing, as it relates to custody actions, is not identical to the standing requirements for challenging an administrative agency ruling. See Moedern v. McGinnis, 70 Wis. 2d 1056, 1067, 236 N.W.2d 240 (1975), for a discussion of standing requirements in administrative agency decisions. Standing in custody cases has generally referred to whether an individual has status to bring an action for custody under the applicable statute. *1009See, e.g., Marshall v. Superior Court, 145 Ariz. 309, 701 P.2d 567 (1985); In re Custody ofBarokas, 109 Ill. App. 3d 536, 440 N.E.2d 1036 (1982); Henderson v. Henderson, 174 Mont. 1, 568 P.2d 177 (1977).
Section 767.24(1), Stats., provides:
Custody and physical placement. (1) GENERAL PROVISIONS. In rendering a judgment of annulment, divorce or legal separation, or in rendering a judgment in an action under s. 767.02(l)(e), the court shall make such provisions as it deems just and reasonable concerning the legal custody and physical placement of any minor child of the parties, as provided in this section.
Section 767.02(l)(e), Stats., provides:
Actions affecting the family. (1) Actions affecting the family are:
(e) Custody.
We have detailed these procedures in numerous cases, including Grams v. Boss, 97 Wis. 2d 332, 338, 294 N.W.2d 473 (1980); Kraemer Bros. v. United States Fire Ins. Co., 89 Wis. 2d 555, 566-67, 278 N.W.2d 857 (1979); Green Springs Farms v. Kersten, 136 Wis. 2d 304, 314-15, 401 N.W.2d 816 (1987).
This conclusion is also consistent with the Legislative Council Note — 1979 to sec. 767.015, Stats., which states:
When the court finds that neither parent is able to provide the child with adequate care or that neither parent is a fit and proper person to have custody of the child, it may transfer custody. . .. (Emphasis added.)
In loco parentis is defined as " [i]n the place of a parent; instead of a parent; charged, factitiously, with a parent's rights, duties, and responsibilities." Black's Law Dictionary, 787 (6th ed. 1990). The literature uses several expressions to describe one who, although not the natural or adoptive parent, stands in the shoes of that parent. See, e.g., Alyson D. v. Virginia M., 1991 WESTLAW 66523 (NY) ("de facto" parent); Nancy S. v. Michele G., 228 Cal. App. 3d 831, 279 Cal. Rptr. 212 (1991) ("psychological" parent); Atkinson v. Atkinson, 160 Mich. App. 601, 408 N.W.2d 516 (1987) ("equitable" parent). These terms are often used synonymously, although there are several legal distinctions. See Nancy S., 228 Cal. App. 3d 831, 279 Cal. Rptr. 212. For purposes of this opinion, we use the term "in loco parentis" to describe an individual with a parent-like relationship with the child for custody purposes, and the expression "equitable parent" to describe an individual who has the rights of a natural parent through equitable estoppel.
Section 767.245(4), Stats. 1985-86, has been renumbered and amended since D.M.M., to include persons such as F.P.R. See current sec. 767.245(1). 1987 Act 355 sec. 38.
It is also difficult to restrict the individuals who may qualify under an in loco parentis status. Housekeepers, prior companions, day-care providers and others could conceivably qualify.
Much of our case law and statutory language reflects the traditional manner in which custody disputes arise, i.e., between two natural parents in a divorce or annulment action. See, e.g., secs. 767.001(1) and 767.24(2), Stats, (which concern joint custody); sec. 767.24(3)(a) (which discusses neither parent); Som-mers, 33 Wis. 2d at 26 (discussing natural parents). Unmarried couples do not fit neatly within the custody statutes because they cannot participate in divorce (secs. 767.07 and .12(2)), annulment (sec. 767.03) or legal separation (secs. 767.07 and .12(2)) proceedings, proceedings which stem from a marital relationship. We have not addressed the question of whether two unmarried individuals can both adopt a child, although other courts have prohibited such a dual adoption under similar statutory schemes. See Adoption of Meaux, 417 So. 2d 522 (La. App. 1982); In re Jason C., 129 N.H. 762, 533 A.2d 32 (1987). The applicable language in sec. 48.82, Stats., indicates only that: "The following persons are eligible to adopt a minor if they are residents of this state: (a) A husband and wife jointly, or either the husband or wife if the other spouse is a parent of the minor, (b) An unmarried adult." Whether two unmarried individuals should be able to adopt (or assume any of the other legal rights and responsibilities now reserved for married individuals) is a legislative question.
Section 767.245(1), Stats., provides:
Visitation rights of certain persons. (1) Upon petition by a grandparent, greatgrandparent, stepparent or person who has maintained a relationship similar to a parent-child relationship with the child, the court may grant reasonable visitation rights to that person if the parents have notice of the hearing and if the court determines that visitation is in the best interest of the child.
In Soergel, this language was inconsequential because the petitioners who sought visitation rights were grandparents, and potentially entitled to visitation rights under either the former or current statutes.
We recognize the rights of adoptive parents based on legal precedents. The dissent passionately but unfairly portrays this decision as one which ignores the rights of children in "nontraditional" relationships. (Bablitch, J., dissenting op. at 1031.) Without support other than its own reading of sec. 767.245, Stats., the dissent concludes that the legislature "could not have intended such an absurd and cruel result," id., apparently having already concluded that the court, rather than a fit legal parent should determine visitation rights in situations such as this.
*1022In arguing for a different reading of sec. 767.245, Stats., the dissent basically asks that we confer the legal status of "parent" on both companions in a "non-traditional" relationship. We refuse to do so for the reasons articulated in this decision. Z.J.H. is not a ”victim[ ] of parental warfare," id. at 1033, because Sporleder is not a "parent." In light of legal precedents, we do not confer that status on her today.
The D.L.H. court was careful to point out that it was not addressing whether the "equitable parent" doctrine operated to elevate the husband in a divorce proceeding from a third-party status to that of a natural parent. D.L.H., 142 Wis. 2d at 617.
Two cases upon which Sporleder relies, A.M.N. v. A.J.N., 141 Wis. 2d 99,414 N.W.2d 68 (Ct. App. 1987); In re Marriage of L.M.S. v. S.L.S., 105 Wis. 2d 118, 312 N.W.2d 853 (Ct. App. 1981), both involved cases where a husband of a wife who bore a child by another man attempted to escape his support obligations. These cases did not attempt to establish an affirmative right to custody, as is the case here.
Another distinguishing factor is the fact that the child in D.L.J. was born into an existing marriage. Many courts have concluded that a man married to a woman at the time she delivers a child fathered by another man may acquire custody of that child under an "equitable parent" theory. See Annotation, Parental Rights of Man Who is Not Biological or Adoptive Father of Child But was Husband or Cohabitant of Mother When Child was Conceived or Born, 84 ALR 4th 655 (1991), and cases cited therein.
For a statement of this balancing test, see 2 Restatement (Second) of Contracts sec. 178 (1979). See also sec. 179 of the Restatement for the bases of public policies against enforcement of an agreement.